In fabricating a semiconductor wafer, plasma etching is commonly used to etch materials, e.g., oxides, etc., from a surface of the semiconductor wafer. To perform the etching, a plasma etch chamber is typically used. The plasma etch chamber is capable of etching selected layers deposited over the semiconductor wafer as defined by a photoresist mask. To perform the etching, the plasma etch chamber receives process gases, and radio frequency (RF) power is applied to one or more electrodes, e.g., an upper electrode, a lower electrode, etc., in the plasma etch chamber. Moreover, other variables, e.g., pressure within the plasma etch chamber, temperature within the plasma etch chamber, etc., are controlled in accordance with a particular desired process. Upon applying a desired amount of the RF power to the electrodes, the process gases in the plasma etch chamber are ionized such that plasma is created within a gap between the upper and lower electrodes.
In order to perform a desired amount of etching of the selected layers of the semiconductor wafer, impedance of plasma in the plasma etch chamber is controlled by manipulating one or more elements, such as, a gap between the upper and lower electrodes, shapes of the electrodes at edges of the electrodes, a flow of gas in region within the plasma etch chamber, etc. However, such manipulation of the elements is difficult to implement and costly.
It is in this context that embodiments described in the present disclosure arise.